55-6
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 55 Configuring a VoIP Network
Understanding How a VoIP Network Works
Analog Trunk Gateway
The Cisco access analog trunk gateways allow the IP PBX to connect to the PSTN or PBX. The gateway
supports up to eight trunks to the PSTN and appears like a phone to the trunk lines coming from the
PSTN. Using this gateway, the IP PBX places an IP call through the PSTN. Similar to the analog station
gateway, the analog trunk gateway provides line echo cancellation and dual tone multifrequency
(DTMF) tone generation and detection. The analog trunk gateway does not provide the ring voltage as
it is not connected to the POTS end devices such as the POTS phones or fax machines. The analog trunk
gateway requires an IP address, is registered with Cisco CallManager in its domain, and is managed by
Cisco CallManager.
To configure the analog trunk gateways, refer to the documentation that shipped with the gateway.
Digital Trunk Gateway
The Catalyst 6500 series 8-port T1/E1 PSTN interface module can support both digital T1/E1
connectivity to the PSTN or transcoding and conferencing. The module requires an IP address, is
registered with Cisco CallManager in its domain, and is managed by Cisco CallManager.
The module software is downloaded from a TFTP server. Depending upon which software you
download, the ports can serve as the T1/E1 interfaces or the ports support transcoding and conferencing.
The transcoding and conferencing functions are mutually exclusive. For every transcoding port in use,
one less conferencing port is available and vice versa.
To configure the 8-port T1/E1 PSTN interfaces, see the
“Configuring VoIP on a Switch” section on
page 55-10
. The module features are listed in
Table 55-2
.
Line echo cancellation (32 ms)
Impedance (600 ohms)
Programmable analog gain, signaling timers
Fax pass-through
SPAN
2
or port mirroring support
FXS Interface Features
Address signaling formats: In-band DTMF
Signaling formats: Loop start
Ringing tone: Programmable
Ringing voltage: Programmable, based on country
Ringing frequency: Programmable, based on country
Distance: 500-ohms maximum loop
1.
DTMF = dual tone multifrequency
2.
SPAN = Switched Port Analyzer
Table 55-1
24-Port FXS Analog Interface Module Features (continued)
Digital Signal Processing Per Port